It has been explained that peptic ulcers like gastric and duodenal ulcers are developed due to collapse of balance between aggressive factors (gastric acid, pepsin, etc.) and defensive factors (blood flow, mucus, mucosal resistance, mucosal protection, etc.). Peptic ulcers are usually subjected to medical treatment, and various medications are applied thereto. The drugs for peptic ulcer therapy may be divided into two types, one being inhibitors of aggressive factors, the other being promoters of defensive factors, and they are used properly according to the type of diseases. Currently, histamine H.sub.2 -blockers (e.g. cimetidine, ranitidine, etc.) are generally used in the clinical stage as inhibitors against aggressive factors. However, it has been reported that there are refractory ulcers, and that the H.sub.2 -blockers possess adverse side effects, such as antiandrogen action and inhibitory action against liver metabolizing enzymes. Recently, it has been found that H.sup.+ /K.sup.+ -ATPase is associated with the final step for acid secretion, and it has been suggested that benzimidazoles having inhibitory action on this enzyme, such as omeprazole, are useful as anti-ulcer drugs. However, palindromia of ulcer is a problem remained unsolved. Furthermore, other problems requiring an improvement exist, such as development of carcinoid, and an interaction with other drugs, which decreases liver clearances for diazepam and fenitoin. On the other hand, it is well-known that the promoters of defensive factors show limited healing rate as compared with the inhibitors of aggressive factors, and that the former provides delayed disappearance of subjective symptom. Thus, anti-ulcer drugs presently available are not satisfactory, and development of promising new anti-ulcer drugs has being desired.
The purpose of the present invention is to find compounds having both inhibitory action against aggressive factors and promoting action on mucosal defensive factors, and to provide more promising anti-ulcer drugs.
European Patent Publication No. 0165545 and U.S. Pat. No. 4,468,400 disclose tricyclic compounds which have similar structures to the compounds of the present invention. However, they don't disclose compounds which have the same substituents as the substituents on the compounds of the present invention. European Patent Publications No. 0033094, No. 0068378 and No. 0204285 disclose non-fused imidazo[1,2-a]pyridines which, on account of their antisecretory and cytoprotective actions, are intended to use for the treatment of ulcer.